The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Patients with ocular pathologies such as optic nerve pathologies and/or retinal pathologies (e.g., patients with glaucoma) have variable localized reduction in visual sensitivity of their visual field. That means that in some areas of their visual field the image is dimmer than other areas. This dimming within the visual field results because more intense illumination is required to stimulate the eye in the affected areas compared to unaffected areas, and is the result of the eye pathology. Patients will describe this dimming as having a cloud or blur over a part of their visual field. When the pathology progresses, the affected areas of the visual field can lose more and more of their ability to see and may eventually become totally blind.
Visual field diagnostic devices have been used to test the visual field sensitivity of a patient by projecting a light that is initially faint and then if the patient does not indicate that he/she is seeing it, the intensity increases more and more until the patient indicates that he/she sees the light. The sensitivity of the projected area is then recorded. If the patient does not see the light even with the maximum illumination intensity, then this area of the visual field is identified as blind.
Refractive errors negatively affect vision. Those refractive errors are caused by irregularities in the refractive elements of the eye. They result in blurry vision that is partly correctable by glass spectacles and contact lenses. That is the reason why some subjects see more than others and some have better quality of vision than others. Spectacles made out of glass as well as contact lenses only come in certain increments and would only correct regular errors of refraction e.g. regular astigmatism. Those regular errors of refraction are called lower order aberrations. Higher order aberrations are errors of refraction that are not correctable by spectacles or by contact lenses. Additionally, higher order aberrations are dynamic and not fixed. They change according to the pupil size, the accommodation state of the eye and direction of gaze.
Current techniques for treating presbyopia include single vision, bifocal and multifocal reading spectacles, and multifocal contact lenses. With the multifocal or bifocal spectacles, the patient will look through specific areas of the glass to get the required correction. With multifocal contact lenses, the light is diffracted into multiple focal points, improving the depth of focus but at the expense of decreasing the quality of vision. All those techniques are not very convenient and limit the near vision.
Double vision results from misalignment of the line of vision of patient. Double vision is dynamic and not static, meaning that it increases and decreases towards one or multiple gazes. So, if the subject has limitation in bringing the right eye outwards then the double vision will increase when the patient is looking to the right and might decrease when the subject is looking to the left.
Anisometropia (unequal refractive power of both eyes of a subject) is not uncommon, especially after eye surgery or trauma. It is one of the indications of cataract surgery per Medicare. Corrective glass spectacles are unable to correct for anisometropia. That is because the corrective glass spectacles produce two images, one to each eye, with unequal sizes (aniseikonia) and the brain could not fuse those two images into a binocular single vision. That problem is simply because the lenses of glass spectacles are either convex, magnify the image or concave, minify the image. The amount of magnification or minification depends on the amount of correction.
Lenses of glass spectacles are either convex, magnify the image or concave, minify the image. That affects the visual field of subjects. Glasses spectacles correct the refractive error of the patient but also produce distortion in the image being viewed.
Subjects with anisocoria have unequal pupil size and that can be congenital, acquired from an eye disease or following surgery or trauma. Those subjects have light sensitivity from a single eye and that eye cannot tolerate the light brightness tolerated by the healthy eye.
There is a need for an optical device that can compensate for the aforementioned visual impairments.